Ingestion of solanine in moderate amounts can cause death. One study suggests that doses of 2 to 5 mg/kg of body weight can cause toxic symptoms, and doses of 3 to 6 mg/kg of body weight can be fatal.[2]

Symptoms usually occur 8 to 12 hours after ingestion, but may occur as rapidly as 10 minutes after eating high-solanine foods.

Solanum glycoalkaloids can inhibit cholinesterase, disrupt cell membranes, and cause birth defects.[3] One study suggests that the toxic mechanism of solanine is caused by the chemical's interaction with mitochondrial membranes. Experiments show that solanine exposure opens the potassium channels of mitochondria, decreasing their membrane potential. This, in turn, leads to K+ being transported from the mitochondria into the cytoplasm, and this increased concentration of K+ in the cytoplasm triggers cell damage and apoptosis.[4]

When potato tubers are exposed to light, they turn green and increase glycoalkaloid production. This is a natural defense to help prevent the uncovered tuber from being eaten. The green colour is from chlorophyll, and is itself harmless. However, it is an indication that increased level of solanine and chaconine may be present. In potato tubers, 30–80% of the solanine develops in and close to the skin, and some potato varieties have high levels of solanine.

Some potato diseases, such as late blight, can dramatically increase the levels of glycoalkaloids present in potatoes. Tubers damaged in harvesting and/or transport also produce increased levels of glycoalkaloids; this is believed to be a natural reaction of the plant in response to disease and damage.

In the 1970s, solanine poisoning affected 78 schoolboys in Britain. Due to immediate and effective treatments, no one died.[6]

Green colouring under the skin strongly suggests solanine build-up in potatoes, although each process can occur without the other. A bitter taste in a potato is another, potentially more reliable indicator of toxicity. Because of the bitter taste and appearance of such potatoes, solanine poisoning is rare outside conditions of food shortage. The symptoms are mainly vomiting and diarrhea, and the condition may be misdiagnosed as gastroenteritis. Most potato poisoning victims recover fully, although fatalities are known, especially when victims are undernourished or do not receive suitable treatment.[6] Fatalities are also known from solanine poisoning from other plants in the nightshade family, such as the berries of Solanum dulcamara (woody nightshade).[7]

Home processing methods (boiling, cooking, frying, and microwaving) have small and variable effects on glycoalkaloids. For example, boiling potatoes reduces the α-chaconine and α-solanine levels by only 3.5% and 1.2%, respectively; the corresponding loss during microwaving is 15%. Deep-frying at 150 °C (302 °F) does not result in any measurable change; significant degradation starts at ∼170 °C (338 °F), and deep-frying at 210 °C (410 °F) for 10 min causes a loss of ∼40%.[9]Freeze-drying or dehydration has little effect.[10]

Some, such as the California Poison Control System, have claimed that tomatoes and tomato leaves contain solanine.[citation needed] However, Mendel Friedman of the federal Department of Agriculture contradicts this claim, stating that tomatine, a relatively benign alkaloid, is the tomato alkaloid while solanine is found in potatoes. Food science writer Harold McGee has found scant evidence for tomato toxicity in the medical and veterinary literature.[11]